Enhanced photoluminescence properties of bismuth sulfide nanocrystals with core-shell Ag@SiO2.

A novel self-assembled hybrid nanocompound consisting of bismuth sulfide nanocrystals (Bi2S3 NCs) and Ag@SiO2 nanoparticles (NPs) is used to study the enhancement of photoluminescence by localized surface plasmon resonance (LSPR). Ag@SiO2 core-shell NPs were prepared by deposition of silica onto the surface of Ag NPs through the sol-gel method and followed by surface modification via 3-aminopropyltriethoxysilane for the coming conjugation with Bi2S3 NCs. We propose the photoluminescence enhancement by the LSPR effect through adjusting the thickness of silica shell and the Ag@SiO2 NP concentration. By modulating the thickness of the silica shell and the concentration of Ag NPs, the maximum enhancement of a 5.7 fold can be reached with the thickness of an SiO2 shell at 22.5 nm. A clear red shift of the emission peaks in the Bi2S3 NCs-Ag@SiO2 NPs hybrid structures is observed. Such a metal-enhanced Bi2S3 quantum dot (QD) fluorescence system may have promising applications in optoelectronic device.

Effects of external magnetic field and out-of-plane strain on magneto-optical Kerr spectra in CrI3 monolayer.

Magnetic semiconductors based on two-dimensional (2D) crystals have attracted attention owing to their intrinsic ferromagnetism and have potential for spintronic devices. Here, full-potential linearized augmented plane wave plus local orbitals method is used to explore the structural, electronic, magnetic, and magneto-optical properties of CrI3 monolayer. Our first-principles calculations show that CrI3 monolayer is a ferromagnetic indirect semiconductor with spin-up and spin-down band gaps of 1.23 and 1.90 eV, respectively, and a magnetic moment of 2.93 [Formula: see text] per Cr atom. Based on the macroscopic linear response theory, we systematically study the influences of external magnetic field and out-of-plane strain on the magneto-optical Kerr effect spectra in CrI3 monolayer. The Kerr rotation of CrI3 monolayer at 1.96 eV photon energy is [Formula: see text], which is consistent with the recent experiments. We find that the Kerr rotation reaches its maximum when the external magnetic field is perpendicular to CrI3 plane, while it is almost zero on turning the magnetic field in the plane. This result as well as the sizable magnetocrystalline anisotropy energy (MAE) of 0.79 meV verifies that CrI3 monolayer has a strong magnetic anisotropy with an out-of-plane easy axis. Further, applying out-of-plane compressive and tensile strain upon CrI3 monolayer, we observe a redshift of the Kerr rotation spectra with the increase of the strain and the peak values of the Kerr rotation increase correspondingly. The rich electronic and magnetic properties, especially the magneto-optical spectra, render CrI3 monolayer a promising 2D magnetic material for applications from sensing to data storage.